Brush manufacturing



Filed Feb. 11, 1958 INVENTOR. JEROME L. BEEN ATT'Y.

" atent Qflice 3,@@8,i93 Patented Nov. 14:, 1961 This invention relatesto the manufacture of brushes and particularly to the dispensing ofresinous compositions for bonding bristles into a setting.

In a typical brush used for applying paint and varnish products, thereare four principal structural components: the cluster of fibers known asthe bristles, the clamping shell known as the ferrule, the setting whichholds the bristles together and within the ferrule and the handle whichis held in the other end of the ferrule. The typical method ofmanufacture comprises placing the cluster of bristles Within the ferruleand dispensing into the ferrule a quantity of a fluid composition whichwhen hardened provides a setting, holds the bristles in place and isadherent to the ferrule.

Bristles may be of animal, vegetable or synthetic origin. Most commonlythey are animal fibers uch as hog bristles and horse hair, but more inrecent years synthetic fibers such as linear polyamides (nylon) andvinylidene chloride (Saran) have become popular because of their moreuniform properties, sterility and increased water resistance.

Ferrules are typically made of tin or nickel plated steel, with someexperimental ferrules being molded from plastics.

The brush setting compositions are typically fluid natural rubber orsynthetic rubber compositions which are formulated so as to cure to ahard, tough, solvent-resistant setting after being dispensed into theferrule holding the clumps of bristles. Even though only comparativelysmall amounts of such compounds are needed in the manufacture ofbrushes, the properties of such compounds are exceedingly important ifthe brush is to be made and to perform successfully.

Thus, the area of bonding surface is dependent upon the depths ofpenetration of the setting compound between the bristles. If penetrationis not uniform, the brush lacks uniform strength characteristics withthe result that either bristles will fall out after a certain amount ofuse or they may be difficult to flex. Further, control of the depth isimportant economically since the cost of a bristle varies exponentiallywith the length of the bristle. Excessive depth is thus more costly thanany advantage gained by extra strength in the setting. Further, withnatural bristles, the shape is not uniform and there is a bulbous rootend, so that a selected mixture of bristles with a resultant uniformpacking factor and cross section is required. Diiferent styles ofbrushes, even of the same bristles, require different viscosities ofsetting compositions with the result that the brush manufacturer must atall times maintain a large stock of different viscosity grades. It isthus an art rather than a science to produce brushes that are uniformand economical.

In addition to these problems, the brush manufacturer is also confrontedwith the difficulty of controlling the temperature where heating isrequired to change the cornposition from a fluid to a tough solid. Heatreduces the flexibility life of natural bristles and renders thesynthetic thermoplastic bristles diflicult to use in a brush. Further,very fine natural bristles artists brushes) are weakened or excessivelydiscolored by heat. Where room temperature curing of compositions hasbeen tried, the change in viscosity due to the initial reaction proceedsso rapidly that proper penetration control is almost impossible with aconsiderable proportion of rejects.

One object of this invention is to provide a process and machine forselectively and controllably providing the desired material to a clusterof bristles. A further object of this invention is to provide such aprocess and machine wherein only three basic materials would be neededfor setting a wide variety of bristle assemblies.

The three materials consist of a first fluid of high viscosity, a secondfluid of low viscosity and compatible with said first fluid, and a thirdfluid. These three fluids are characterized in that at least one of themis a roomtemperature curable brush-setting composition and at least oneof the other two is a hardening composition reactive at room temperaturewith each such brush setting composition. The three fluids are furthercharacterized in that a mixture of the three fluids in selectedproportions provides a hardenable mix of the desired viscosity. Further,the mix is substantially solventless; such being achieved by usingsubstantially solventless brush-setting compositions and a minimum ofany necessary solvent in a hardener component.

In carrying out this invention, a separate source for each of the threefluids is provided in, for example, a separate reservoir. The high andlow viscosities are chosen in accordance with the requirements of thebrushmaker as to his shallowest and deepest penetration brushes. Thehigh viscosity Would be higher than the viscosity the brush-maker wouldrequire for the short penetration in his shallowest penetration brusheswhile the low viscosity would be lower thatn the viscosity required forthe deep penetration in his deepest penetration brushes. The process ofthe invention comprises simultaneously supplying from each fluid sourceto a single chamber a separately selected and controlled amount of eachfluid. In the chamber, the three volumes are substantiallyinstantaneously mixed and then immediately totally dispensed to thedesired location such as a cluster of bristles in a cavity such as aferrule.

In one form of this invention, two of the fluids are substantiallysolventless room-temperature curable fluid brush setting compositionscompatible with one another, one being of the low viscosity and theother being of the high viscosity. The third fluid source comprises thehardener composition reactive with each other fluid. In the discussionbelow, Examples 1 and 2 are with reference to this form of theinvention.

The selection of the proper high and low viscosity is governed by thebrush makers needs, since some brush makers have a wider range ofpenetration requirements than others. In general, however, the viscosityof approximately 300 centipoises for one composition and approximatelyl50,000200,-000 centipoises for the other composition would meet thenormal requirements of most brush manufacturers.

In practicing this invention, any suitable positive displacementmetering device may be used. However, it is preferable to use a thinstable-liquid system (such as oil) for the metering, with diaphragmchambers or the equivalent for translating the oil movement to resinmovement, because of the practical difficulties of directly handlingviscous tacky hardenable materials in many common pumping and meteringsystems. Thus, each reservoir is provided with separately controllablemeans for expelling on a predetermined time bias a selected quantity offluid into the mixing chamber simultaneously with the expelling ofrequired volumes from the other two reservoirs. In this fashion, a shotis practically instantaneously formed, mixed and delivered to the brushsetting, thus avoiding any aging problem or temperature control problem.The setting is usually allowed to harden at room temperature, but may beheated to accelerate hardening where such heating would not bedeleterious to the particular bristles or setting.

The fluid resinous compositions usable in this invention include fastsetting potting compounds such as liquid phenolic casting compounds andcompounds based on epoxy resins of diiferent molecular weights. Epoxyresin casting compounds are especially preferred because of excellentbonding to bristles and ferrule and low shrinlo age. By use ofappropriate fillers, the viscosity can be made high while theuse of lowmolecular weight epoxy resins will yield low viscosity liquids. For suchepoxy resins a large number of aliphatic polyamine hardeners areavailable such as, for example, diethylene triamine. Compounds otherthan epoxy resins may be used; as, for example, polyester castingresins, which ordinarily require an organic peroxide as the hardener butwhich are not as rapidly curable at room temperature. Likewiseconventional, previously described substantially solventless plasticrubbery compositions may be used for natural bristles although usuallysome heating may be required. It has been found that although otherpotting com pounds can be used, that the compounds containing a majorquantity of epoxy resins are substantially superior as regards adhesivestrength to both ferrule and bristle and freedom from cracks and splits.However, any previously successful brush compound can be used with thisinvention with uniform controllable penetration.

One embodiment of this invention is described below and is illustratedin the drawing wherein FIGURE 1 is a schematic diagram of an apparatuscapable of carrying out the process of this invention.

The illustrated apparatus comprises a closed reservoir in which fluidhardener is stored, closed reservoir 11 in which low viscosity fluidresinous composition is stored and closed reservoir 12 in which highviscosity fluid resinous composition is stored. The reservoirs havesingle open conduits 13, 14 and 15 leading to a Y connection wherein onebranch 15, 16 and 17 leads into a pressure vessel 18, 19, and 20 and theother leg of the Y through a conduit 21, 22, and 23. The conduits 21,22, and 23 connect to the input of a mixer-dispenser 24, which can befor example a high-speed (3000 rpm.) homogenizer such as an Eppenbachmixer) or a low-speed helix mixer (200 rpm.) or any similar devicecapable of handling heavy viscous material. Each pressure vessel 18, 19and 20 contains a flexible but impervious diaphragm 25, 26 and 27 so asto divide each vessel into two isolated compartments 18a and 18b, 19aand 19b, and 20a and 20b. Each B" compartment is connected to a separateconduit 28, 29, and 30 which connects to one side of a.solenoid-operated 3-way valve 31, 32, 33. Each valve is connected to theoutput side of a separate positive displacement proportioning gear pump34, 35, 36 and to the input of a separate oil reservoir 37, 38 and 39.The output side of each oil reservoir is connected to the input side ofthe pump. Check valves 40 are provided to prevent back fiow. The pumpsoperate continuously and the valves operate simultaneously, either bymanual switch or ordinary electric time control means. When the valvesare actuated, flow goes to B compartments, otherwise to oil reservoirs.The control of speed of each pump such as by a variable resistanceprovides the proper ratio of volumes, while control of the time ofduration that the valves open to the pressure reservoirs provides theproper shot volume.

The volume of each oil reservoir is substantially equal to the volume ofits corresponding pressure vessel. Thus, both the resin and oil systemsare filled with the appropriate compounds so that there is no air in thesystem and each pump is adjusted as to speed for proper ratio, and thesolenoids time-controlled for proper control of shot volume. When thevalves are opened to the pressure vessels, each pressure vessel receivesan additional selected increment of oil, which causes the diaphragm tomove, thus displacing to conduit 21, 22, and 23 corresponding identicalincrements of compound fluid which are simultaneously received, mixedand totally dispensed by the mixer 24. The mixer is constantly movingand has an appropriately small volume to mix and dispense the shots. Theconduits are full but the mixer is empty so that the volumes to bedisplaced are already adjacent to the openings in the mixer. Suitabletemperature control can be provided by jacketing the mixer, conduits,and vessels.

The term epoxy resin as used herein refers generally to the polymericreaction products of polyfunctional halohydrins such as epihalohydrinswith polyfunctional hydrogen-donating reactants such as polyfunctionalphenols, alcohols and amines. Common epoxy resins include the reactionproducts of epichlorohydrin with biophenol. The preparation of epoxyresins is described in many US. patents including 2,500,449; 2,444,333;2,528,932; 2,500,- 600; and 2,467,171. Shell Epon Resins 834, 828 and815 are examples of commercial epoxy potting resins of varyingviscosity.

Examples of typical epoxy resin compounds which can be used in theinvention are given below:

Example I Shell Epon Resin 834 Micronized sil ca .20

The above materials, measured by weight, were charged separately into aBaker-Perkins internal mixer, and mixed at room temperature untiluniform. The result was a high viscosity paste material which barelyflows at room tem- The above two ingredients were charged into a Baker-Perkins mixer and stirred until uniform. The result was a free-flowingat room temperature, light-amber colored liquid with a sticky feel.

A compound of Example I was charged to the reservoir 11, andWasidentified as the heavy component. The compound represented byExample 11 was charged into reservoir 12 and identified as lightcomponent. The third reservoir 10, identified as the hardener reservoir"was charged with diethylenetriamine. A batch of hogbristled, unbondedbrushes was obtained from a manufacturer, of uniform composition andmake-up, and characteristic of the average setting design typical of theindustry. The dispensing device Was set so as to dispense a mixtureconsisting of parts by weight of heavy component (Example I), and 8parts by weight of hardener diethylene triamine. This mixture wascharged into the ferrules of brushes of this uniform test batch. Theaverage depth of penetration attained was ,4 of an inch, as measuredafter 24 hours at room temperature, at which time the resin-hardenermixture had set to a hard, tough, amber-like resinous composition. Thisamount of penetration was not considered adequate to support and bondthe bristles within the brush, especially under the subse quentmechanical strains to be imposed.

The machine was set so that in another group of brushes dispensed amixture consisting of 100 parts of thin component (Example II) and 8parts of the same hardener. In this same batch of test brushes: thepenetration observed after allowing 24 hours at room temperature forhardening, was over one inch, with jagged spikes of resin having floweddown the bristle length to the bottom of .the bristles (about threeinches, in this case). This indicated excessive penetration.

The machine was then set to operate delivering a mixture consisting of60 parts of the heavy component, 50 parts of the thin component, and 8parts of the hardener. When observed in the same brushes after 24 hoursat room temperature hardening, penetration was uniform and attained adepth of of an inch, considered to be just correct for these brushes.There were no points where "MA MI the compound had spiked down to thebottom of the bristles.

It was found that the repetitive operation of this same machine with thesame components in the chambers, under various conditions of initialcomponent temperatures and ambient room temperatures, provided onlyslight variations in penetration depth. These could readily and rapidlybe corrected by very slight changes in the proportions of the heavy andlight components. In addition, in actual tests in brush factories, wherethe whole range of normal variation were encountered between lots ofbrushes it was found that simple manipulation of the proportions of theheavy and light components permitted the operator to rapidly set themachine to deliver the proper penetration depth of compound. One testused is the heat-freeze or gel test Where the material is allowed topenetrate at room temperature for 20 hours and then heated at 150 C. forone hour. The setting is then examined for penetration depth,uniformity, spiking, adhesion, and splits. It is required of the brushmanufacturer only that he maintain the reservoirs with the two resinouscomponents and the one harder component, These are the only materialsnecessary for him to stock, regardless of the variation in type of brushrequired.

In addition to the above desribed form of the invention wherein the highand low viscosity fluid compositions comprise reactive brush settingcompositions and the third fluid is a room-temperature hardener for suchcompositions, there is another form of this invention wherein the highand low Viscosity compositions comprise room-temperature hardenercompositions, while the third fluid comprises the brush settingcomposition reactive with the hardener. In this second form of theinvention the liquid hardener, which is usually quite thin, can beincreased in viscosity by admixture of inert, viscosity-increasedingredients such as thermoplastic resins, soluble soap and colloidalminerals. Examples of these are /2-second cel lulose-acetate-butyrate,calcium stearate and colloidal silica. In addition, materials which arenon-reactive with the hardener but reactive with the brush settingcomposition can be used in admixture with the hardener to provide highand low viscosity components. An example of this, where an epoxy resinis the base for setting composition, is the use of polyamide resins inadmixture with an epoxy hardener such as diethylenetriamine.

In this second form of the invention, it is desirable that the third orreactive resin fluid be of average viscosity and the first and secondfluids be on the high and low ends of the desired viscosity range. Theother aspects of this second form of the invention are similar to thefirst form and the same sort of apparatus can be used.

As an example of this second form using epoxy resin as the reactiveresin of the brush setting composition is given below:

Example 111 A mixture of ten parts by weight of diethylenetriamine andone part by weight of calcium stearate are charged into a Baker-Perkinsmixer and stirred until uniform to provide a high viscosity paste whichbarely flows at room temperature. This high viscosity mixture is chargedinto reservoir 11. Into reservoir 12 is charged diethylene triamine (thethin liquid hardener) and into reservoir 10' is charged a quantity ofShell Epon Resin 828 which is a thin low molecular weight epoxy resin.The dispensing device is then arranged to prow'de a mixture of ten partsof the material in reservoir 12 (low viscosity fluid), ten parts of thefluid in reservoir 11 (high viscosity fluid) and 100 parts of thereactive brush setting composition in reservoir 10*. When dispensed intothe same type of bristle examples as described in previous examples,substantially identical results are obtained.

I claim:

1. In a process for manufacturing brushes in rapid succession wherein afluid brush setting composition is delivered to a cluster of bristlesspaced within a cavity and then hardened to form the setting, the stepsof providing a first separate fluid supply of a viscosity higher thanrequired for setting any of the brushes desired to be made, a secondseparate fluid supply of a viscosity lower than required for setting anyof the brushes desired to be made and compatible with said first fluid,and a third separate fluid supply and a plurality of successive cyleseach consisting of providing a cluster of bristles within a cavity,simultaneously delivering a separately selected volume from each saidfluid supply to a single chamber, substantially instantaneously mixingsaid volumes in said chamber and delivering the total resultant mixtureto said cavity, and allowing the resultant setting .to harden; saidfluid supplies being characterized in that one consists of aroom-temperature curable fluid brush setting composition, one comprisesa hardener composition reactive at room temperature with each such brushsetting composition in the mixture and the remaining fluid supply is amember of the group consisting of a room-temperature curable fluidbrush-setting composition and a hardener composition reaction at roomtemperature with each brush-setting composition in the mixture; saidfluid supplies being further characterized in that said mixture issubstantially solventless.

2. The steps of claim 1 wherein the fluid brush-setting compositionscontain epoxy resins as the major reactive component and the hardener isan aliphatic amine.

3. In a process for manufacturing brushes in rapid succession wherein afluid brush-setting composition is delivered to a cluster of bristlesspaced within a cavity and then hardened to form the setting, the stepsof providing a first separate fluid supply consisting of a substantiallysolventless room-temperature-curable fluid brush-setting composition ofa viscosity higher than required for setting any of the brushes desiredto be made, a second separate fluid supply consisting of a substantiallysolventless roomtemperature curable fluid brush-setting compositioncompatible with said first fluid but of a viscosity lower than requiredfor setting any of the brushes desired to be made, and a third separatefluid supply consisting of a hardener composition reactive at roomtemperature with each said first and second fluids and a plurality ofsuccessive cycles each consisting of providing a cluster of bristlesspaced within a cavity, simultaneously delivering a separately selectedvolume from each said fluid supply to a single chamber, substantiallyinstantaneously mixing said volumes in said chamber and delivering thetotal resultant mixture to said cavity, and allowing the setting toharden; said fluids being characterized in that said resultant mixtureis substantially solventless.

4. In a process for manufacturing brushes in rapid succession wherein afluid brush setting composition is delivered to a cluster of bristlesspaced within a cavity and then hardened to form the setting, the stepof providing a first separate fluid supply consisting of a substantiallysolventless room-temperature curable fluid brush-setting composition, asecond separate fluid supply consisting of a hardener compositionreactive with said brush composition and having a viscosity higher thanrequired for setting any of the brushes desired to be made, and a thirdseparate fluid supply consisting of a hardener composition reactive withsaid brush-setting composition, compatible with said second fluid supplyand of the viscosity lower than required for setting any of the brushesdesired to be made and providing a plurality of successive cycles eachconsisting of providing a cluster of bristles within a cavity,simultaneously delivering a separately selected volume from each saidfluid supply to a separate chamber, substantially instantaneously mixingsaid volumes in said chamber and delivering the total resultant mixtureto said cavity, and allowing the setting to harden; said fluids beingcharacterized in that said resultant mixture is substantiallysolventless.

(References on following page) References Cited in the file of thispatent 2,5 17,456 2,604,362 UNITED STATES PATENTS 2,621,369 2,317,110Person Apr. 20, 1943 ,67 56 2,392,542 Matuszak I an. 8, 1946 5 2,764,5652,406,732 Hardman Aug. 27, 1946 2,917,065

8 Wherrett Aug. 1, 1950 Sugerman et a1 July 22, 1952 Gantz et a1 Dec.16, 1952 Ullman Apr. 6, 1954 Hoppe et a1. Sept. 25, 1956 Monk Dec. 15,1959

